Simple Li-Fi Transmitter Receiver Circuit

Think internet is like a light and not a radio wave, then this Simple Li-Fi Transmitter Receiver Circuit do the same thing like that.

This article tell how to make simple Li-Fi system to send and get data using light.

Here, transmitter uses bright LED and normal transistor to send signal and receiver catch signal with light sensor like solar cell and make signal strong so we can hear from speaker.

Also, this project is easy to understand and how Li-Fi work but it does not replace Wi-Fi.

Transmitter Working:

Parts List:

Components	Values	Quantity
Resistors	2Ω 1W, 4.7k 1/4 watt, 1k 1/4 watt	1 each
Capacitor	Electrolytic 2.2µF 25V	1
Semiconductors	Transistor 2N2222	1
	LED White 1 Watt	1

First, use the 2N2222 transistor as a common emitter amplifier and use the 4.7k and 1k resistors to form a voltage divider at the base, called VBias.

When audio connects in transmitter it changes transistor output and this change make 1 watt LED light blink same like audio signal.

Capacitors 2.2µF on transistor base help keep audio clear and they stop DC from going through and if we use higher voltage like 12V and put resistor with LED to control current then it works right.

Transmitter Construction:

• To make transmitter use 2N2222 transistor and set it like common emitter amplifier.
• LED light become bright or dim with audio signal which changes same like sound.
• Put capacitors at transistor base because they block DC and keep audio clean.
• Also, if using high voltage like 12V then add one resistor with LED to limit current.
• We can give audio from MP3 player, phone or microphone with preamp.

Receiver Working:

Parts List:

Components	Values	Quantity
Resistors	100Ω 5W, 33Ω 5W	1 each
Capacitors	Electrolytic 100µF 25V	1
Semiconductors	Transistor 2N3055	1
	Transformer 12-0-12V	1
	Speaker 8Ω 2.5 Watt	1
	Solar Panel any small size	1

Receiver use solar cell and 2.2μF capacitor in series and this solar cell give voltage that change with light which is sensitive to light around.

This changing voltage goes to amplifier 2N3055 transistor or other similar type and this is very sensitive so it can catch weak audio signal.

Also, then sound is louder and goes to speaker so we hear it clearly.

How to Make Receiver:

• First, use 6V solar cell and 3V also okay with 2.2μF capacitor in series and connect with amplifier.
• Amplifier can be any good one that has high sensitivity.
• Test the circuit in dark room with no lights nearby to work better.

Formulas:

Audio amplifier can use one transistor and one transformer.

Below is formula:

Impedance Ratio = (Np / Ns)²

here,

• Np is the number of turns in primary coil
• Ns is the number of turns in secondary coil

Note:

To make good audio amplifier use correct parts and build it carefully and for better sound use multistage amplifier circuit with more than one amplifier stage.

Overall Circuit Operation:

First, this circuit works in low light and avoids interference from electric lights due to its design.

LED may flicker a little which human eye cant see it.

Also, even if we do not see it LED brightness changes when audio goes in transmitter.

Then solar cell in receiver catches small voltage changes and then amplifier make sound from it.

So to test, turn on both transmitter and receiver and give audio to transmitter and change the volume.

Hence, speaker on receiver should give clear sound.

Finally, we can build simple Li-Fi circuit for wireless sound if we learn and follow these steps.

Steps:

• Make transmitter and receiver circuits one by one.
• First, connect 1 watt LED in parallel with solar cell.
• Then power both circuits and adjust transmitter volume.
• Also, give audio input to transmitter.
• After that, in dark room listen if speaker is ON and receiver gives clear sound.
• Then try using photodiode and change amplifier to LM386 circuit.
• Circuit will still work good and we must try different parts too.

Important Notes:

LED may flash a little and this mean something is not working right.

When WE apply audio, the LED brightness changes slightly and the change is too small for the eyes to see.

Also, if there is no audio then LED stays always ON and this is because input capacitor blocks DC signal.

Solar cell can feel small voltage changes but ignore steady DC and capacitor helps send only the audio signal.

So use sensitive amplifier to make circuit work better.

Conclusion:

To conclude, we can build Simple Li-Fi Transmitter Receiver Circuit and receiver by following these steps.

This circuit gives new way to send sound in places with low light, so try different parts to get best result for our need.

References:

Datasheet 2N3055